#include <bits/stdc++.h>
using namespace std;
using ll = long long;
using pii = pair<int, int>;
#define rep(i, a, b) for (int i = (a); i <= (b); i++)
#define per(i, a, b) for (int i = (a); i >= (b); i--)
#define endl '\n'
const int N = 1e4 + 5;

int n, m;
int a[N];

int main() {
  ios::sync_with_stdio(0), cin.tie(0), cout.tie(0);
  cin >> n >> m;
  rep(i, 1, n) cin >> a[i];
  priority_queue<int, vector<int>, greater<int>> pq;
  rep(i, 1, m) pq.push(a[i]);
  rep(i, m + 1, n) {
    int t = pq.top();
    pq.pop();
    pq.push(t + a[i]);
  }
  int ans = 0;
  while (pq.size()) {
    ans = max(ans, pq.top());
    pq.pop();
  }
  cout << ans;
  return 0;
}